Cell Biology: Microtubules and Plasma Membrane
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What is the primary function of microtubules in eukaryotic cells?

  • Segregate chromosomes during cell division (correct)
  • Make up the plasma membrane
  • Aid in cell movement
  • Anchor organelles

    • Eukaryotic cells do not possess membranous organelles.

    False

    What term describes the structure of the plasma membrane?

    fluid mosaic

    The __________ regulates the exchange of materials with the environment.

    <p>plasma membrane</p> Signup and view all the answers

    Match the following cytoskeleton components with their characteristics:

    <p>Microfilaments = Made of actin and myosin, aid in cell movement Intermediate filaments = Provide tensile strength, anchor organelles Microtubules = Made of tubulin, rapidly assemble and disassemble Centrosome = Organizing center for microtubules in animal cells</p> Signup and view all the answers

    What is the primary function of mitochondria?

    <p>Energy processing</p> Signup and view all the answers

    Aerobic cellular respiration occurs only in the presence of carbon dioxide.

    <p>False</p> Signup and view all the answers

    What is the process of dividing the nucleus and its contents called?

    <p>Mitosis</p> Signup and view all the answers

    DNA replication occurs during the _____ stage of interphase.

    <p>Synthesis</p> Signup and view all the answers

    Match the following phases of mitosis with their descriptions:

    <p>Prophase = Condensation of chromatin Metaphase = Alignment of chromosomes at the equatorial plate Anaphase = Separation of sister chromatids Telophase = Formation of two new nuclei</p> Signup and view all the answers

    Which enzyme is crucial for adding nucleotides during DNA replication?

    <p>Polymerase</p> Signup and view all the answers

    Meiosis results in four identical gametes.

    <p>False</p> Signup and view all the answers

    What are telomeres and why are they important?

    <p>Telomeres are DNA sequences at the ends of chromosomes that protect them from degradation.</p> Signup and view all the answers

    Mitochondria are _____ inherited.

    <p>maternally</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Chromatid = Half of a replicated chromosome Centromere = Pinched center of a chromosome Kinetochore = Site of attachment for the mitotic spindle Cytokinesis = Division of cytoplasmic components</p> Signup and view all the answers

    What is the summary reaction formula for aerobic cellular respiration?

    <p>C6H12O6 + 6O2 → 6CO2 + 6H2O + 36-38 ATP</p> Signup and view all the answers

    Interphase consists of three stages: G1, G2, and M phase.

    <p>False</p> Signup and view all the answers

    How many chromosomes do gametes contain compared to somatic cells?

    <p>Half</p> Signup and view all the answers

    Which of the following proteins change shape to move solutes across the membrane?

    <p>Carrier proteins</p> Signup and view all the answers

    Active transport requires metabolic energy, typically in the form of ATP.

    <p>True</p> Signup and view all the answers

    What is the primary function of the sodium-potassium (Na+-K+) pump?

    <p>To maintain higher concentrations of Na+ outside and K+ inside the cell.</p> Signup and view all the answers

    The movement of substances out of cells is called exocytosis.

    <p>exocytosis</p> Signup and view all the answers

    Match the terms with their descriptions:

    <p>Endocytosis = Movement into cells via vesicles Exocytosis = Movement out of cells via vesicles Phagocytosis = Engulfing of molecules or invaders Osmosis = Movement of water across a semi-permeable membrane</p> Signup and view all the answers

    What type of transport involves moving two solutes simultaneously?

    <p>Secondary active transport</p> Signup and view all the answers

    Transcytosis involves the movement of substances into cells followed by their movement out of cells.

    <p>True</p> Signup and view all the answers

    Define osmosis.

    <p>The movement of water from low solute concentration to high solute concentration across a semi-permeable membrane.</p> Signup and view all the answers

    When both solutes flow in the same direction during secondary active transport, this is called symporters_.

    <p>symporters</p> Signup and view all the answers

    Which statement is true regarding cyanide's effect on active transport?

    <p>Cyanide inhibits ATP production and consequently all active transport</p> Signup and view all the answers

    What percentage of the membrane is made up of phospholipids?

    <p>75%</p> Signup and view all the answers

    Saturated fatty acids increase membrane fluidity.

    <p>False</p> Signup and view all the answers

    Define membrane fluidity.

    <p>The ability for the lipid bilayer to move proteins and lipids laterally within the layer.</p> Signup and view all the answers

    Cholesterol serves as a _____ buffer for membrane fluidity.

    <p>fluidity</p> Signup and view all the answers

    Match the following membrane components with their functions:

    <p>Integral proteins = Span the entire membrane Peripheral proteins = Bound to the membrane by electrostatic interactions Glycoproteins = Help with cell identification Receptors = Bind specific molecules to send signals</p> Signup and view all the answers

    Which type of molecules can travel through the membrane without assistance?

    <p>Nonpolar molecules</p> Signup and view all the answers

    Membrane permeability allows all substances to pass through easily.

    <p>False</p> Signup and view all the answers

    What role do integral membrane proteins play?

    <p>They span the entire membrane and can facilitate transport.</p> Signup and view all the answers

    The _____ model describes the structure of biological membranes as a mosaic of proteins and lipids.

    <p>fluid mosaic</p> Signup and view all the answers

    How does increasing the temperature generally affect diffusion?

    <p>Increases the rate of diffusion</p> Signup and view all the answers

    Peripheral proteins are embedded within the lipid bilayer.

    <p>False</p> Signup and view all the answers

    What is facilitated diffusion?

    <p>Diffusion of substances across a membrane through specific transmembrane proteins.</p> Signup and view all the answers

    The _____ gradient is established when there are different concentrations of a substance across the membrane.

    <p>concentration</p> Signup and view all the answers

    What effect do unsaturated fatty acids have on membrane fluidity?

    <p>Increase fluidity</p> Signup and view all the answers

    What type of diffusion occurs through aquaporins?

    <p>Facilitated diffusion</p> Signup and view all the answers

    Hypertonic solutions have a lower solute concentration than inside the cell.

    <p>False</p> Signup and view all the answers

    What happens to a red blood cell when placed in a hypotonic solution?

    <p>It swells and may burst.</p> Signup and view all the answers

    Cells in __________ solutions will experience no net water movement.

    <p>isotonic</p> Signup and view all the answers

    Match the type of solution with its description:

    <p>Hypertonic = Higher solute concentration than inside the cell Hypotonic = Lower solute concentration than inside the cell Isotonic = Equal solute concentration as inside the cell Osmolarity = Total concentration of solutes in a solution</p> Signup and view all the answers

    Which solution would be best for rehydration after severe dehydration?

    <p>Hypotonic solution</p> Signup and view all the answers

    Somatic cells divide by meiosis to produce identical daughter cells.

    <p>False</p> Signup and view all the answers

    Why is it important for intravenous (IV) fluids to be isotonic to blood?

    <p>To maintain osmotic balance.</p> Signup and view all the answers

    What is the primary function of the centrosome in animal cells?

    <p>Organization of microtubules</p> Signup and view all the answers

    Cilia are long bundles of microtubules used for cell movement.

    <p>False</p> Signup and view all the answers

    What structure in the nucleus is responsible for making ribosomal subunits?

    <p>nucleolus</p> Signup and view all the answers

    The _____ is all of the DNA in an organism.

    <p>genome</p> Signup and view all the answers

    Match the following organelles with their primary functions:

    <p>Centrosome = Organizes microtubules Golgi Complex = Modifies and sorts proteins Lysosome = Breaks down cellular waste Peroxisome = Detoxifies substances</p> Signup and view all the answers

    What type of endoplasmic reticulum is involved in lipid synthesis?

    <p>Smooth endoplasmic reticulum</p> Signup and view all the answers

    Ribosomes are made of rRNA and proteins and are responsible for synthesizing lipids.

    <p>False</p> Signup and view all the answers

    What is the function of the Golgi complex?

    <p>Modifies, sorts, and packages proteins</p> Signup and view all the answers

    Ribosomes translate mRNA into _____

    <p>proteins</p> Signup and view all the answers

    What triggers the export of proteins from the rough endoplasmic reticulum?

    <p>Vesicle formation</p> Signup and view all the answers

    Defective lysosomes can lead to disorders like Tay-Sachs disease.

    <p>True</p> Signup and view all the answers

    What role do tRNAs play during translation?

    <p>Carry amino acids matching mRNA codons</p> Signup and view all the answers

    The _____ membrane is continuous with the nuclear envelope.

    <p>rough endoplasmic reticulum</p> Signup and view all the answers

    What function is NOT associated with lysosomes?

    <p>Photosynthesis</p> Signup and view all the answers

    Study Notes

    Cell Structure and Function

    • Cells vary in shape and size, with approximately 200 different cell types in the human body.
    • Cells are the basic unit of life, organizing functions through organelles, which behave as “little organs.”
    • Eukaryotic cells have membranous organelles; prokaryotic cells do not.

    Organelles in Eukaryotic Cells

    • The plasma membrane is a flexible barrier that separates internal and external environments, regulating material exchange and facilitating intercellular communication.
    • The cytoplasm includes all content between the plasma membrane and nucleus, providing an environment for chemical reactions.

    Cytoskeleton

    • Composed of microfilaments, intermediate filaments, and microtubules, aiding cell shape, stability, and movement.
    • Microfilaments (actin and myosin) support structure and facilitate movement.
    • Intermediate filaments provide tensile strength and anchor organelles.
    • Microtubules (made from tubulin) segregate chromosomes during cell division and form motile structures like cilia and flagella.

    Centroles and Cell Movement

    • The centrosome organizes microtubules and contains centrioles, crucial for mitotic spindle formation.
    • Cilia (short) and flagella (long) enable movement in various cells, including respiratory tract cells and sperm.

    Nucleus

    • Contains DNA within a double membrane structure called the nuclear envelope, perforated by nuclear pores.
    • Houses the nucleolus, responsible for ribosomal subunit production.

    DNA Organization

    • DNA exists as chromatin (loose form) for transcription and can be tightly wound into chromosomes for cellular division.
    • The genome encompasses all DNA in an organism.

    Ribosomes and Protein Synthesis

    • Ribosomes are composed of rRNA and proteins, critical for translating mRNA to proteins.
    • The central dogma of biology describes DNA transcription to mRNA, followed by translation to protein.
    • Ribosomes can bind multiple transcripts, allowing for the rapid production of many proteins.

    Endoplasmic Reticulum (ER)

    • The rough ER (rER) has ribosomes for protein synthesis, continuous with the nuclear membrane.
    • The smooth ER (sER) synthesizes lipids, stores calcium, and detoxifies drugs.

    Golgi Complex

    • Modifies, sorts, and packages proteins received from the rER into vesicles for transport.
    • Cisternae are membranous folds facilitating these processes.

    Lysosomes and Peroxisomes

    • Lysosomes are membrane-bound sacs containing digestive enzymes for breaking down cellular materials.
    • Peroxisomes oxidize molecules, metabolizing fatty acids and detoxifying harmful substances.

    Mitochondria

    • Bounded by two membranes, crucial for ATP production through aerobic cellular respiration.
    • Mitochondria are maternally inherited and have their own DNA, replicating independently.

    Cell Division

    • Somatic cells undergo mitosis and cytokinesis, with interphase stages G1, S (DNA replication), and G2 (organelle replication).
    • Mitosis proceeds through prophase, metaphase, anaphase, and telophase, ultimately leading to cytokinesis.

    Telomeres

    • Telomeres protect chromosome ends from degradation; they shorten with age.
    • Telomerase maintains telomere length in cancer cells, contributing to rapid cell division.

    Meiosis

    • Meiosis produces gametes (haploid cells) through two rounds of division: Meiosis I and II.
    • Crossing over occurs in Meiosis I, allowing genetic variation.

    Membrane Structure and Fluidity

    • The plasma membrane is a fluid mosaic model with a phospholipid bilayer, cholesterol, and embedded proteins.
    • Membrane fluidity allows for protein and lipid movement, essential for many cellular functions.

    Transport Mechanisms

    • Simple diffusion allows nonpolar molecules to move across membranes passively without energy input.
    • Facilitated diffusion utilizes ion channels and carrier proteins to transport charged or polar substances down their concentration gradients.
    • Active transport requires energy to move substances against their concentration gradient.

    Membrane Permeability

    • Membranes selectively permit certain molecules; gases like O2 and CO2 pass easily, while polar molecules require specialized channels.

    Summary of Cell Functionality

    • Cells maintain homeostasis through various organelles, structures, and processes, ensuring efficient interaction with their environment and division for growth and repair.### Active Transport
    • Moves solutes against concentration gradients across membranes.
    • Sodium-potassium (Na+-K+) pump maintains high Na+ concentration outside the cell and high K+ concentration inside the cell.
    • Na+-K+ pump operates through ATP hydrolysis, changing its shape to transport ions.

    Types of Active Transport

    • Primary active transporters directly use ATP to move solutes against their gradients.
    • Secondary active transporters utilize electrochemical gradients established by primary active transporters to move solutes.
    • Simultaneous transport by secondary active transporters categorizes into:
      • Symporters: both solutes move in the same direction.
      • Antiporters: solutes move in opposite directions.

    Inhibition of Active Transport

    • Cyanide inhibits ATP synthesis in mitochondria, thus stopping all active transport processes.

    Vesicular Transport

    • Vesicles transport products between organelles.
    • Endocytosis: movement into cells via vesicles.
    • Exocytosis: movement out of cells, termed secretion in some instances.
    • Both processes require ATP hydrolysis.
    • Transcytosis involves endocytosis followed by exocytosis to move substances through cells.

    Types of Endocytosis

    • Receptor-mediated endocytosis: imports specific molecules.
    • Phagocytosis: “eating” of substances or invaders by immune cells, leading to lysosomal digestion.
    • Pinocytosis: “drinking” of dissolved solutes, also known as bulk-phase endocytosis.

    Osmosis

    • The movement of water from low solute concentration to high solute concentration across a semi-permeable membrane.
    • Aquaporins facilitate the efficient movement of water across membranes.

    Tonicity and Cell Behavior

    • Solutions may vary in solute concentration affecting cell behavior:
      • Hypertonic: higher solute concentration outside the cell, causing water to exit.
      • Hypotonic: lower solute concentration outside the cell, leading to water entering the cell.
      • Isotonic: equal solute concentration inside and outside the cell, resulting in no net water movement.

    Clinical Application of Tonicity

    • Intravenous (IV) fluids are typically isotonic to blood to maintain osmotic balance.
    • Hypertonic solutions can lead to cell crenation, while hypotonic solutions can cause cell swelling.

    Osmolarity

    • Total concentration of solute particles in a solution, determining how a cell behaves in that solution.

    Cell Division

    • Somatic cells divide by mitosis, producing two identical daughter cells.
    • Reproductive cells divide by meiosis, resulting in four nonidentical gametes.

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    Description

    This quiz tests your knowledge on the primary functions of microtubules in eukaryotic cells and the structure of the plasma membrane. Explore the characteristics of various cytoskeleton components and understand their roles in cellular processes. Evaluate your understanding of these key concepts in cell biology.

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